Thermoregulatory strategies of three reclusive lizards (genus Xantusia) from the Baja California peninsula, Mexico, under current and future microenvironmental temperatures.

The thermal quality of the habitat is key for the regulation of body temperature in terrestrial ectotherms and, therefore, permits them to carry out their fundamental biological activities. In thermally heterogeneous environments, ectotherms might follow different behavioral or physiological strategies to maintain their body temperature within biologically adequate boundaries, for which they depend on microhabitat selection. These aspects are, thus, relevant in the context of habitat degradation and land-use change. In this study, we characterized the thermal ecology of three lizard species (genus Xantusia) that differ in microhabitat use along the Baja California peninsula, Mexico. We made three predictions: (1) the three species will follow different thermoregulatory strategies according to habitat thermal quality; (2) the thermal requirements and tolerances of these species will match the environmental or microenvironmental thermal conditions; and (3) due to their habitat and range restriction, the species studied will be highly vulnerable to climate change. Our results indicate the existence of thermoregulatory mechanisms in Xantusia to face thermal heterogeneity, including behavioral thermoregulation by choosing different microhabitats, shifts in activity periods, and adaptation to particular high thermal quality microhabitats. Furthermore, despite their association to specific microhabitats and specialized physiology, the studied species will not be adversely affected by climate change, as the increased microenvironmental temperatures will lead to a higher habitat thermal quality and lower costs of thermoregulation. However, we do not discard other indirect adverse effects of climate change not considered in this study.

Sexual Dimorphism and Foraging Trips of the Laysan Albatross (Phoebastria immutabilis) on Guadalupe Island.

Sexual dimorphism in the Laysan albatross (Phoebastria immutabilis) on Guadalupe Island was evaluated during the breeding seasons of 2015-2018 by measuring and comparing 10 morphological attributes: cranial length, bill length, nostril length, cranial width, bill height, bill width, tarsus length, closed wing length, opened wing length, and wingspan length in reproductive adults (n = 135). Males were larger than females across all traits (Student's t-test, p < 0.05, p < 0.05). We created a logistic model using stepwise regression to predict sex based on morphological variables. This model indicated four significant morphological predictor variables (z < 0.05) and was able to successfully predict the sex of P. immutabilis individuals in more than 90% of the cases. Based on these predictor variables, a web app was developed to determine the sex of the Laysan albatross in the field, providing a non-invasive method for rapid data collection that reduces costs and handling times while improving conservation efforts. We tracked Laysan albatross (n = 36) during breeding seasons and found no significant differences between females and males for either trip length (GLMM, F = 0.017, DF = 1, 1, p = 0.917 > 0.05) or maximum trip distance (GLMM, F = 0.374, DF = 1, 1, p = 0.651 > 0.05). Our results suggest that both sexes show a strong preference to travel to highly productive coastal waters northeast of the breeding colony that are influenced by the California Current. The present research will serve to establish a baseline to protect this species on Guadalupe Island and highlights the importance of understanding sexual dimorphism in at-risk seabird species.

Occurrence of Batrachochytrium dendrobatidis in anurans of the Mediterranean region of Baja California, México.

Chytridiomycosis is caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd) and is regarded as one of the most significant threats to global amphibian populations. In México, Bd was first reported in 2003 and has now been documented in 13 states. We visited 33 localities and swabbed 199 wild-caught anurans from 7 species (5 native, 2 exotic) across the Mediterranean region of the state of Baja California. Using quantitative PCR, Bd was detected in 94 individuals (47.2% of samples) at 25 of the 33 survey localities for 5 native and 1 exotic frog species. The exotic Xenopus laevis was the only species that tested completely negative for Bd. We found that remoteness, distance to agricultural land, and elevation were the best positive predictors of Bd presence. These are the first Bd-positive results for the state of Baja California, and its presence should be regarded as an additional conservation threat to the region's native frog species.